Arc regulator



May 12; 1936. K @RENKERT 2 @4 ARC REGULATOR Filed Aug. 18, 1935 2 Sheets-Shec l I N V E NTO R. /6754 Ema/M5227? ATTORNEY.

May 152 R936. K. BRENKERT ARC REGULATOR Filed Aug. 18, 1933 2 Sheets-Sheet 2 I NVEN TOR. 76% 47745587 ATTORNEY.

Patented May 12, 1936 UNITED STATES PATENT OFFICE.

ARC REGULATOR Application August 18,

3 Claims.

The present invention pertains to a regulator designed particularly for feeding the electrodes in the arc lamp of a projection. machine. The regulator described herein may be used either 5. with alternating or direct current and is. designed to overcome certain of the difi'iculties incident to an alternating current machine, as will presently be described. The feeding mechanism is driven by a motor which is controlled by a switch em- 10 bodied in the regulator.

In connection with an alternating current machine, the objects of the invention are, generally, to provide a regulator and switch that operate definitely and positively to open and close the feeding motor circuit at definite current or voltage values, without rapid make or break of the circuit due to the alternation of the current strength and without the. noise that would accompany such rapiclmake and break.

In an arc regulator it is desirable to feed the electrodes by anelectric motor and to control the running and stopping of the motor by a switch automatically actuated by the changing characteristics of. the arc. As the feeding mechanism must maintain the electrodes a certain distance apart and as the arc current or voltage is proportional to this distance, the motor switch is made. dependent on the arc circuit and is controlled by an electro-magnet in series or shunt with the. are for operating the switch which is in series with the motor. The electro-magnet must therefore be permanently wired to the arc circuit and must be so constructed as to open and close the motor switch according to the volt- 35 age or current value in the arc circuit and hence according to the arc gap.

As the feeding mechanism has varying. friction characteristicsv due to temperature. changes, degreeof cleanliness and lubrication, it is desirable 40 to. apply to the motor its full running voltage in order 'toovercome these friction variations. To accomplish. this. result, the switch controlling the motor circuit must make. good contact to start the motor at full power and. to break contact completely to stop the motor when the electrodes have been fed. to. the correct spacing. According to theinvention, these requirements are satisfied by a liquid type switch, such as a mercury switch.

Another object of the invention is to provide a regulator adapted to throw the switch one way or the other within small variations in the arc current strength, such as 2% or 3% for example It has been found that this degree of sensitiveness requiresthe use of an internal armature for the electro-magnet, that is, an armature which ro- 1933, Serial No. 685,691

tates or reciprocates within the magnetic field as distinguished from an external armature attracted to the magnet by a force whichvaries inversely as the square of its distance from the magnet at a given magnet strength. In the internal type of armature, as used in thisinvention, the pull on the armature is more nearly uniform, regardless of its position, at a. given magnet strength.

The regulator according to the present invention embodies also a device, such as a spring, acting on the armature in opposition to the magnetic field. Thus, a given field. strength is necessary to balance the spring, and at this strength the device may be said to be in equilibrium. In opera,- tion, however, either the spring or the magnetic field is overbalanced by the other, resulting in moving and holding the switch definitely in open or closed position, as the case may be. Thus, when one of the electrodes has been fed near enough to the other, the increased current in the field windings of the magnet is sufiicient to turn the armature against the spring and move the spring to open position, thereby stopping the motor. Conversely, at a given separation of the electrodes, in balance, the spring overcomes the action of the magnetic field and moves the switch to closed position.

The invention is fully disclosed by way of example in the following description and in the accompanying drawings, in which:-

Figure 1 is a. rear end view of a projector equipped with a regulator according to the invention;

Figure 2 is a corresponding side view;

Figure 3 is a wiring diagram of the apparatus;

Figure 4 is an elevation of the regulator;

Figure 5 is a section on the line 5-5 of Figure 4;

Figure 6 is a section on theline 6'-6 of Figure 4;

Figure '7 is a section on the line 1-1 of Figure 4.

Reference to these views will now be made by use of like characters which are employed to designate corresponding parts throughout.

In Figures 1 and 2 is: illustrated the usual housing I of a projector, the back of which carries a motor 2 for feeding the carbons. The feed mechanism is well known in the art and is indicated here by the numeral 3. Also on the back of the housing and below the motor 2 is a housing 4 which contains the regulator for controlling the actuation of the motor 2.

The housing 4 is insulated from the housing I by an interposed panel 5 of suitable material, and the housing 4 may also include a detachable portion 6 for access to the interior. A frame piece I is mounted in the housing 4 preferably parallel to the rear wall thereof for the support of certain of the interior parts as will presently appear. A block 9 is held against the inner side of the member 5, and against this block is mounted a U- shaped set of laminations 9 for producing a magnetic field therebetween. Bosses ID extend from the plate 1 into contact with the outer laminations. The assembly is maintained by bolts H passed through the bosses, laminations and members 8 and 5 and held by nuts I2 and I3 bearing against the latter. Further, bolts l4 are passed through the lower part of the plate 1 and through the lower ends of the laminations and are held by nuts l5 as shown more clearly in Figure 5.

Pivot screws I6 are mounted in the members I and 3 and are in axial alignment as may be seen in Figure 5. On the screws is journaled a pivot stud At opposite sides of the stud the laminations 9 are concaved at l8 to permit rotation of a laminated armature I9 mounted on the stud.

On the stud l1 and outwardly of the laminated structure is mounted a rocker arm 20 having an outwardly extending lower end 2|. The plate I has a lug 22 in which is adjustably mounted a screw 23, and a coil spring 24 extends from the screw to the lower end of the rocker arm 20 as shown more clearly in Figure 6. Lugs 25 extend outwardly from the plate I at opposite sides of the extended end 2| and contain adjustable screws 26 to limit the movement of said end under the conditions presently to be described.

On the top of the arm 29 is mounted a mercury switch 21 held by a suitable clip 28 attached to the arm. A binding post 29 is carried by the panel 5, and to this post is secured a conductor 30 which is coiled successively around the groups of laminations as indicated by the numeral 3| in Figures 4 and 6. Another binding post 32 is also secured to the panel 5 (Figure 7) and receives the end of the second coil 3|. The post 32 also serves to support a conducting bracket 33 on which is mounted a coiled resistor 34 by means of a bolt 35 passed axially therethrough and fastened to the bracket.

One of the points or contacts 33 of the mercury switch is joined by a conductor 3! to the bolt 35, with a washer 38 insulating the conductor from the resistor wire. The other point 35 is joined by a conductor 39 to a binding post 39 and thence to the upper end of the resistor 34. The lower end of the resistor is joined by a conductor 40 to the bracket 33 as may be seen in Figure '7.

Further, with reference to the structure of the device, a threaded boss 4|, (Fig. 5) is secured to the plate 5 and extends between the sets of laminations as may be seen in Figure 6. A screw 42 passed through the detachable cover 6 is threaded in the boss 4| to secure the cover in position.

With reference now to the wiring already described and to the diagram shown in Figure 3, one of the current mains 43 is connected to another post 44 on the panel 5 and thence to the electrode 45. Another conductor 45 extends from the post 44 through the motor 2 and to one of the points 36 of the mercury switch. The motor may, however, be supplied by an independent line, but in either case the control switch for the motor is operated by the current flowing in the electrodes.

The main 41 is attached through the post 32 and conductor 40 to the lower end of the resistor and through the bolt 35 and conductor 31 to one of the switch points 36. The other switch point is joined by the conductor 38 to the motor connection post 39 and then to the upper end of the resistor, from which it will be seen that the resistor is connected across the switch for a purpose which will presently appear. From the post 32, current passes through both coils 3| to the post 29 which is connected to the carbon 48.

In the operation of the device, it will be evident that the coils 3| are permanently in the circuit of the are, preferably but not necessarily in series.

There is always a magnetic field between the sets of laminations tending to turn the armature l9 against the tension of the spring 24. The tendency of the spring is to tilt the armature and the mercury switch to a position wherein the latter closes the circuit of the electrode feeding motor 2. The spring may be replaced by any other means opposing the electro-magnet such as, for example, another electro-magnet.

It will be understood that the strength of the current between the electrodes varies inversely as the distance between the electrodes. The strength of the current in the coils 3|, and hence the strength of the magnetic field pulling the armature against the spring 24, likewise is proportional to the arc current. When the are current reaches a given value, the magnetic field is strong enough to turn the armature |9 against the action of the spring 24, thereby opening the mercury switch and stopping the motor 2 and the feeding of the carbons. The particular current value required to open the switch is determined by adjustment of the spring 24 by means of the screw 23.

As the carbons burn away after the feed mechanism has stopped, the length of the arc increases and its current strength drops until the spring 24 returns the mercury switch to the closed position. If the switch opens at 80 amperes, it closes at approximately '78 amperes, due to drag in the movement of the parts because of inertia and friction. This range of two amperes between reversals is desirable in order to prevent fluttering or rapid making and breaking of the motor circuit at the critical current value. The drag may be intro duced, for example, by adjusting the pivot screws IE to produce a given degree of friction on the ends of the stud H.

The weight of the mercury has a similar effect on the reversal of the switch, for its inertia must be overcome prior to a reversal, and when overcome, is shifted in favor of the new position.

The motor 2 takes about 1 amperes while running, but draws about 2 /2 amperes in starting. It will be recalled that the motor starts on weakening of the magnetic field, and the high starting current further weakens the field, permitting the spring 24 to hold the mercury switch more firmly in closed position. This is in the nature of a snap action tending to hold the switch closed at the instant the motor starts. In like manner, the stopping of the motor on strengthening of the magnetic field returns current to the coils 3| to strengthen the field still further and hold the switch positively in open position.

The resistor 34 passes about ampere. It will be seen by the wiring diagram that this amount of current always flows through the motor but is not sufiicient to operate it. Because of this arrangement the mercury switch need carry only ampere, and when the switch is closed, the motor receives the necessary 1 amperes to turn it. Arcing at the switch is thereby reduced and the life of the switch is prolonged. Also, the use of a lighter and more sensitive switch is made possible.

The regulator is designed for use with alternating as well as direct current. In an alternating current apparatus, the armature l9 and the mercury switch are constantly in vibration in keeping with the cyclic alternation of the current. Under such conditions, a switch having rigid contacting parts would not only make and break the motor circuit several times a second but would also produce vibratory noise which is very undesirable. The mercury switch mounted in this device, may be regarded as having a resilient contact portion, namely the mercury, which maintains contact notwithstanding the cyclic vibration. In other words, although the mercury may be seen to vibrate, it does not alter the condition of the switch determined by the strength of the magnetic field. Also, this vibration produces no noise in the apparatus.

The use of a magnetic regulator with direct current, operating by variations in the arc characteristics, is well known. In adapting this type of regulator to alternating current, it was found that the switch contacts constantly vibrate with the cyclic alternation of the current, causing rapid make and break of the motor circuit with the result that the motor is constantly running. The noise created by the rapid making and breaking is also objectionable. These difiiculties are overcome in the present device by the absence of rigid parts striking against each other. For example, the armature moves noiselessly as distinguished from the clattering that would occur with an external type of armature, and the liquid type of switch opens and closes noiselessly as distinguished from a switch having only rigid contact members.

Although a specific embodiment of the invention has been illustrated and described, it will be understood that various alterations in the details of construction may be made without departing from the scope of the invention, as indicated by the appended claims.

What I claim is:

1. In combination with a pair of spaced electrodes, a pair of field magnets disposed oppositely to each other and permanently in circuit with said electrodes, an armature rotatably mounted between said magnets, so that the magnetic pull thereon is substantially equal in opposite directions perpendicularly from its axis of rotation, a motor for feeding at least one of said electrodes, a liquid type switch carried by said armature and movable thereby to open and closed positions, said switch governing the circuit of said motor, and quick-acting biasing means tending to move said armature in opposition to the action of said magnets thereon, whereby said motor circuit is made and opened promptly at critical current values in said electrodes and unaffected by cyclic vibration of said armature, said switch being silent during such vibration.

2. In combination with a pair of spaced electrodes, a pair of field magnets disposed oppositely to each other and permanently in circuit with said electrodes, an armature rotatably mounted between said magnets and movable between its extreme positions substantially within the confines of the pole surfaces of said magnets so that the magnetic pull thereon is substantially equal in opposite directions perpendicularly from its axis of rotation, a motor for feeding at least one of said electrodes, a liquid type switch carried by said armature and movable thereby to open and closed positions, said switch governing the circuit of said motor, and quick-acting biasing means tending to move said armature in opposition to the action of said magnets thereon, whereby said motor circuit is made and opened promptly at critical current values in said electrodes and unaffected by cyclic vibration of said armature, said switch being silent during such vibration.

3. In combination with a pair of spaced electrodes, a pair of field magnets disposed oppositely to each other and permanently in circuit with said electrodes, an armature rotatably mounted between said magnets and movable between its extreme positions substantially within the confines of the pole surfaces of said magnets so that the magnetic pull thereon is substantially equal in opposite directions perpendicularly from its axis of rotation, a motor for feeding at least one of said electrodes, a liquid type switch carried by said armature and movable thereby to open and closed positions, said switch governing the circuit of said motor, and spring biasing means tending to move said armature in opposition to the action of said magnets thereon, whereby said motor circuit is made and opened promptly at critical current values in said electrodes and unaffected by cyclic vibration of said armature, said switch being silent during such vibration.

KARL BRENKERT. 

